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Hydrogen is one of the most promising alternate fuels due to its clean burning characteristics and better performance as compared to fossil fuels. In addition to the need for finding effective solutions to the problem of air pollution from combustion processes, increasing pressure is being placed to find alternative fuel to replace the rapidly depleting petroleum fuels. Numerous research works have been carried out on using hydrogen as a fuel in Spark Ignition (SI) engine. However the major drawback of using hydrogen in a SI engine is the reduction in power output of the engine by about 30% in addition to problems like pre ignition, back fire and knocking at higher loads. Hence the use of hydrogen in a SI engine is limited.

Diesel engines are the main prime movers for public transportation vehicles, stationary power generation units and for agricultural applications. Hence it is very important to find a best alternate fuel, which emits fewer pollutants into the atmosphere from diesel engines. In this regard hydrogen is receiving considerable attention, as an alternative source of energy to replace the rapidly depleting petroleum resources. Its clean burning characteristics provide a strong incentive to study its utilization as a possible alternate fuel. Hydrogen injection along with selective catalytic converter shows very attractive results both from the performance and emissions point of view. A maximum reduction in oxides of nitrogen (NOx) of 74% is achieved for a (ratio of flow rate of ammonia to the flow rate of NO) of 1.1 with a marginal reduction in efficiency. The reduction in both hydrocarbon (HC) and NOx emission is one of the major advantages of Selective Catalytic Reduction (SCR) system.

During the last decade the use of alternative fuels for diesel engine has received renewed attention. The interdependence and uncertainty of petroleum based fuel availability and environmental issues, most notably air pollution are among the principal forces behind the movement towards alternative sources of energy. The main pollutants from the conventional hydrocarbon fuels are unburned / partially burned hydrocarbon (UHC), carbon monoxide (CO), oxides of Nitrogen (NOx), smoke and particulate matter. These emissions are harmful to human, animal and plant life. Emissions from automobiles are currently a dominant source of air pollution representing 70 % of carbon monoxide, 41 % of oxides of Nitrogen (NOx), 38 % of hydrocarbon emissions globally. In addition 25 % of the man made CO2 emissions globally adds to the green house effect, which results in global warming. In the present investigation hydrogen is used in a diesel engine in the dual fuel mode using diesel as an ignition source.

The world is confronted with the two major crisis namely, fossil fuel shortage and environmental degradation. The non edible vegetable oil and its methyl ester have been considered a promising option. In the present investigation, tests were carried out to analyze the combustion process of Rubber Seed Oil Methyl Ester (RSOME), Rubber Seed Oil (RSO) and compared with diesel. The engine performance and exhaust emissions were also studied for better understanding of the combustion process. It was observed that the premixed combustion phase of RSOME combustion was more intense than that of RSO due to its lower ignition delay. It was also noted that the ignition delay and combustion duration decreased with RSOME, which indicated higher heat release resulting in higher thermal efficiency than RSO. The brake thermal efficiency is 26.53% with RSO, 27.89% with RSOME and 29.93% with diesel at full load. The peak pressure increased by 2.3 bar for RSOME compared to that of RSO.

In the context of fossil fuel crisis and ever increasing vehicle population, the search for alternative fuel has become necessary. Vegetable oil can be used as an alternative fuel for the diesel engine operation. How ever, engine performance is inferior to diesel due to their higher viscosity. The higher viscosity of vegetable oil causes improper atomization of fuel during injection resulting in incomplete combustion. This leads to smoky exhaust in a diesel engine. While pre-heating of vegetable oil, it was found that viscosity reduces exponentially with temperature. The high temperature of the exhaust, which is otherwise wasted, can be used to preheat the vegetable oil. For this purpose a heat exchanger has to be designed. It was observed that the rubber seed oil (RSO) requires a heating temperature of 155°C to bring down its viscosity to that of diesel.

Several researches were carried out on biodiesel combustion, performance and emissions till today. But very few research talks about the chemistry of biodiesel that affects the diesel engine operation. Biodiesel is derived from vegetable oils or animal fats, which comprises of several fatty acids with different chain length and bonding. This paper presents affect of biodiesel molecular weight, structure (Cis and Trans), and number of double bond on diesel engine operation characteristics. For this experiment we have selected three type of biodiesel with different molecular weight and number of double bond. All these three biodiesel selected for our test was prepared and analyzed for fuel properties according to the standard. These biodiesel are tested in a constant speed diesel engine, which developing 4.4 kW power and compared with diesel fuel.

Hydrogen is expected to be one of the most important fuel in the near future to solve greenhouse problem and to save conventional fuels. In this study, a Direct Injection (DI) diesel engine was tested for its performance and emissions in dual-fuel (Hydrogen-Diesel) mode operation. Hydrogen was injected into the intake port along with air, while diesel was injected directly inside the cylinder. Hydrogen injection timing and injection duration were varied for a wider range with constant injection timing of 23° Before Injection Top Dead Centre (BITDC) for diesel fuel. When hydrogen is used as a fuel along with diesel, emissions of Hydro Carbon (HC), Carbon monoxide (CO) and Oxides of Nitrogen (NOX) decrease without exhausting more amount of smoke. The maximum brake thermal efficiency obtained is about 30 % at full load for the optimized injection timing of 5° After Gas Exchange Top Dead Centre (AGTDC) and for an injection duration of 90° crank angle.

The internal combustion engines, have already, become an indispensable and integral part of our present day life style, particularly in the transportation and agricultural sectors. Unfortunately the survival of these engines has, of late, been threatened due to the problems of fuel crisis and environmental pollution. Therefore, to sustain the present growth rate of civilization, a non-depletable, clean fuel must be expeditiously sought. Hydrogen exactly caters to the specified needs. Hydrogen, even though “Renewable” and “clean burning”, does give rise to some undesirable combustion problems in an engine operation, such as backfire, pre-ignition, knocking and rapid rate of pressure rise. The present investigation compares the performance and emission characteristics of a DI diesel engine with gaseous Hydrogen as a fuel inducted by means of Carburation and Timed Port Injection (TPI) techniques along with diesel as a source of ignition.

A diesel engine was operated with karanja oil, bio-diesel obtained from karanja oil (BDK) and diesel as pilot fuels while LPG was used as primary fuel. LPG supply was varied from zero to the maximum value that the engine could tolerate. The engine output was kept at different constant levels of 25%, 50%, 75% and 100% of full load. The thermal efficiency improved at high loads. Smoke level was reduced drastically at all loads. CO and HC levels were reduced at full load. There was a slight increase in the NO level. Combustion parameters indicated an increase in the ignition delay. Peak pressure and rate of pressure rise were not unfavorably affected. There was an increase in the peak heat release rate with LPG induction. The amount of LPG that could be tolerated with out knock at full load was 49%, 53% and 61% on energy basis with karanja oil, BDK and diesel as pilots.

Intensified search for alternative fuels is the main interest across the world due to the impact of fossil fuel crisis, ever increasing vehicle population and oil price and stringent emission norms. On the other hand, the disposal of waste tyres from automotive vehicles becomes complex. Apart from alternative biomass derived fuels like Ethanol, Methanol, Hydrogen, Vegetable oils etc, the new sources for alternative fuels are also appreciable. In this context, Pyrolysis of solid wastes is currently receiving renewed interest. The disposal of waste tyres can be simplified to some extent by Pyrolysis. In this paper, the properties of the pyrolysis oil derived from the waste automobile tyres were analysed and compared with the petroleum products and pure rubber pyrolysis oil. Also, Tyre pyrolysis oil-Diesel blends were used as alternate fuel in a four stroke Diesel Engine without any modification in the engine and the performance and emission characteristics have been studied.

Diethyl Ether (DEE) is a significant component in a blend or as a complete replacement for diesel fuel. The presence of smoke in the diesel engine exhaust is an indication of poor combustion due to so many reasons. Nevertheless with increasing concern for the effect of air pollution on the environment, animal and plant life, particularly in road transport, vehicle exhaust emissions have in recent years been subjected to increasingly stringent regulations. A novel way of approaching in this direction is utilization of LPG in direct injection Diesel engine as a fuel with DEE as an ignition enhancer. This paper reports on the study of performance and emissions characteristics in a four stroke, 3.7 kW, single cylinder, DI diesel engine on homogeneous charge compression ignition mode (HCCI).

Vehicular emissions contribute nearly two-third of the environmental pollution. The increasing usage of personal transportation and higher emissions from the tail pipe contribute significantly to the climate change. Though catalytic converters and other regulatory measures have brought down the emission levels, it is a serious concern about addressing the problems of depleting fossil fuel sources and the green house gas emissions. The effective use of ethanol either as a neat fuel or as a mixture with gasoline has proved technically feasible and environmentally acceptable. Electric Vehicle (EV) which is a Zero emission vehicle is yet to be accepted due to its poor drivability range. Hence Hybrid Electric Vehicles is emerging as an alternate solution that overcome the disadvantages of EV's and the existing prime movers can suitably be combined with the electric drive to produce optimal results.

In the efforts for developing relatively clean and efficient burning fuels, attention is being focused on various gaseous fuels. Gaseous fuels in diesel are possible in dual fuel operation. It is well known that the operation of LPG-Diesel dual fuel engine at lower loads suffers from lower thermal efficiency and higher unburned percentages of fuel. To overcome this drawback, a new methodology has been adopted in the present work, namely, isomerisation of gaseous fuels. Experiments have been conducted by using Al2O3/Pt as an isomerisation catalyst. It is concluded that thermal efficiency at light loads can be improved significantly and emission levels reduced at all loads.

Vegetable oils can be directly used in compression ignition engines without any modification. A dual fuel engine was run using vegetable oils as primary and pilot fuels. Small quantities of orange oil were inducted along with air and ignited after compression by a pilot spray of Jatropha oil. The energy share of orange oil was varied till 35% of the total. Methyl ester of Jatropha oil and diesel were also used as pilot fuels for comparison. Dual fuel operation with orange oil induction reduced the smoke level and improved the thermal efficiency with all pilot fuels. However, hydrocarbon and carbon monoxide emissions were higher. Ignition delay was also increased. Methyl ester of Jatropha oil showed inferior performance than diesel. Performance with Jatropha oil was still inferior. On the whole it is concluded that the use of Jatropha oil and methyl ester of Jatropha oil as pilot fuels and orange oil as the inducted fuel will lead to reduced smoke levels and improved thermal efficiency.

Use of vegetable oils in diesel engines results in increased smoke and reduced brake thermal efficiency. Dual fuel engines can use a wide range of fuels and yet operate with low smoke emissions and high thermal efficiency. In this work, a single cylinder diesel engine was converted to use vegetable oil (Jatropha oil) as the pilot fuel and methanol as the inducted primary fuel. Tests were conducted at 1500 rev/min and full load. Different quantities of methanol and Jatropha oil were used. Results of experiments with diesel as the pilot fuel and methanol as the primary fuel were used for comparison. Brake thermal efficiency increased in the dual fuel mode when both Jatropha oil and diesel were used as pilot fuels. The maximum brake thermal efficiency was 30.6% with Jatropha oil and 32.8% with diesel. Smoke was drastically reduced from 4.4 BSU with pure Jatropha oil operation to 1.6 BSU in the dual fuel mode.

Experiments were conducted to assess the relative effects of swirl (by using a masked intake valve and by providing swirl grooves on the piston crown) and squish on the performance, emission and combustion characteristics of a lean burn engine operating on liquefied petroleum gas (LPG) at a compression ratio of 10.5 under 20% and 100% throttle opening conditions. The swirl produced by the masked intake valve configuration at 100% throttle opening resulted in improved thermal efficiency and reduced HC emission, cyclic variations, ignition delay & combustion duration as compared to swirl groove piston and enhanced squish piston. The lean misfire limit was extended and there was no increase in the NO level at any given power output. At 20% throttle with high squish, under lean mixture conditions, combustion is even better than the masked valve configuration.

The performance of a conventional, carbureted, two-stroke spark-ignition (SI) engine can be improved by providing moderate thermal insulation in the combustion chamber. This will help to improve the vaporization characteristics in particular at part load and medium loads with gasoline fuel and high-latent-heat fuels such as methanol. In the present investigation, the combustion chamber surface was coated with a 0.5-mm thickness of partially stabilized zirconia, and experiments were carried out in a single-cylinder, two-stroke SI engine with gasoline and methanol as fuels. Test results indicate that with gasoline as a fuel, the thin ceramic-coated combustion chamber improves the part load to medium load operation considerably, but it affects the performance at higher speeds and at higher loads to the extent of knock and loss of brake power by about 18%. However, with methanol as a fuel, the performance is better under most of the operating range and free from knock.

The use of alcohol-gasoline blends enables the favorable features of alcohols to be utilized in spark ignition (SI) engines while avoiding the shortcomings of their application as straight fuels. Eucalyptus and orange oils possess high octane values and are also good potential alternative fuels for SI engines. The high octane value of these fuels can enhance the octane value of the fuel when it is blended with low-octane gasoline. In the present work, 20 percent by volume of orange oil, eucalyptus oil, methanol and ethanol were blended separately with gasoline, and the performance, combustion and exhaust emission characteristics were evaluated at two different compression ratios. The phase separation problems arising from the alcohol-gasoline blends were minimized by adding eucalyptus oil as a co-solvent. Test results indicate that the compression ratio can be raised from 7.4 to 9 without any detrimental effect, due to the higher octane rating of the fuel blends.

The main objective of the present research work is to utilise the higher amounts of exhaust energy of the LHR engines. Three vegetable oils(neem oil, rice bran oil and karanji oil) were tested in the low heat rejection engine. An electrical heater was used to heat the thick vegetable oils or the air and the results were studied. the electrical heater energy was correlated with the energy available in the exhaust of the LHR engine, so that the electrical heater can be replaced by a heat exchanger in the actual engine. The three vegetable oils, without heating, indicated a lower brake thermal efficiency of 1-4% when compared with the standard diesel engine. When these thick vegetable oils are heated and used in LHR engines the brake thermal efficiency improves. For every vegetable oil, there is an optimum temperature at which it gives the best performance.

As alternate fuels, ethyl and methyl alcohols stand out because of the feasibility of producing them in bulk from plentifully available raw materials. In the present work, ethanol is used as the only fuel, in the standard and Low Heat Rejection(LHR) diesel engines by adopting three different methods. In the first method, ethanol as the sole fuel was used in the LHR engine with normal metal glowplug and in the second method spark plug assistance was used to initiate combustion. In the third method, ethanol was used as the sole fuel in a LHR engine and a ceramic glow plug was used to initiate combustion. The engine was tested for performance and emissions for the above three methods of 100% ethanol operation in both the standard and LHR diesel engine and the results are compared. The spark plug assisted ethanol operation in the LHR engine gave the highest brake thermal efficiency and the lowest emissions.